412 THE FERTILISATION OF FLOWERS. [PART III. 
differences. In the short-styled flowers, the calyx is longer and 
narrower, the corolla is longer and has a much larger and more con- 
spicuous limb; the ovary is smaller; the nectaries larger and more 
rich in honey than in the long-styled flower. In the Alps humble- 
bees and Rhingia and Bombylius act as cross-fertilising agents 
for this species, as they do for P. officinalis in the Lowlands (609). 
Hildebrand denies that this plant is heterostyled: it is possible 
that he made his observations on cultivated examples, and that 
Fic. 137.—Pulmonaria angustifolia, L . 
A.—Long-styled flower. 
B.—Ditto, in section. 
C.—Ditto. ov, ovary; n, nectary; gr, style (x 43). 
D.—Short-styled flower. 
E.—Ditto, in section (x 14). 
F.—Ditto (x 43). 
.—Limb of the corolla of a short-styled flower, cut off close above the anthers, to show the 
protecting hairs (x 49). 
Q 
there is in them, as Darwin has shown in the case of Primula 
sinensis, a return to the homostylic condition (609). 
Darwin found the long-styled though not the short-styled 
flowers of this species absolutely barren when illegitimately fer- 
tilised ; he gives several reasons for considering that this dimorphic 
plant is in a transition-stage, tending to become dicecious (167). 
304. PULMONARIA OFFICINALIS, L.—This species also is di- 
morphic. Honey is secreted by the white, basal part of the ovary, 
lodged in the lower portion of the tubular corolla, and sheltered 
from rain by a ring of hairs placed in the tube at the place where 
it widens out. In the short-styled flowers, the anthers stand at 
the mouth of the corolla (whose tube is 10 to 12 mm. long); the 
stigma stands half-way up the tube, on astyle 5 to 6 mm. long: in 
the long-styled flowers these positions are reversed, the style being 
10 mm. long, and the anthers, being attached by very short fila- 
ments to the corolla, 5 mm. from the base of the flower. Since the 
corolla widens slightly at its mouth, insects with a proboscis 8 mm, 
